Method and a device for manufacturing a tool and a tool made by the method

ABSTRACT

A rotary tool such as a helix drill and an end mill for example, is manufactured by forming a blank by an extrusion process, and then sintering the blank. During the extrusion, a mixture is passed through a die which provides a cylindrical shape to the outer peripheral surface of the mixture. A plurality of jaws are disposed downstream of the die for conducting the mixture. Each jaw includes a helical ridge for engaging the outer surface of the extrudate to cause a helical groove to be formed therein which constitutes a chip flute in the tool. During the extrusion, the jaws are moved away from the mixture to terminate formation of the chip groove, whereby a shank portion of the tool is formed.

This application is a divisional of application Ser. No. 09/586,974,filed on Jun. 5, 2000.

FIELD OF THE INVENTION

The present invention relates to a method and a device for manufacturinga tool and a tool made by the method.

PRIOR ART

It is previously known through for example International Publication WO98/28455 to press material powder, such as wolfram carbide (WC) togetherwith cobalt (Co), between a punch and a die, and subsequently to sinterthe material such that the binder metal is melted and binds the carbidesto form tool material for chip removing machining. The known techniquebrings about a plurality of drawbacks. The powder give off dust and theformed green body (pressed but not sintered material) will not endurehandling to any degree. Furthermore the chip flutes must be ground andthe method requires time and energy. The problems have partly beensolved by the injection molding of hard metal mixed in a carrier such asindicated in U.S. Pat. No. 5,947,660. The method of injection mouldingbrings a high degree of freedom concerning geometry but brings costlyinvestments in moulds.

Through U.S. Pat. No. 4,779,440 a tool is previously known for forming ablank for a helix drill. An extruded drill blank having chip flutes ofconstant pitch along the circumference of the blank is obtained byheating a hard metal powder to extrusion temperature, pressing theheated powder blank under high energy consumption through a spacedefined by a mandrel and a nozzle while rotating the blank. The blank isguided during the extrusion past a helical ridge provided at the insideof the nozzle, to shape helical chip flutes along the blank as the blankrotates. A drawback of the known technique is that the chip flutes areobtained along the entire length of the blank.

OBJECTS OF THE INVENTION

One object of the present invention is to provide a method, a device anda tool, whereby the drawbacks of the known technique are eliminated.

Another object of the present invention is to provide a method and adevice whereby the lengths of the chip flutes can be determined.

SUMMARY OF THE INVENTION

These and other objects have been achieved by a method and apparatus formanufacturing a tool as well as a tool made by the method.

The method of manufacturing a rotary tool for chip removing machiningcomprises the steps of:

-   -   A. providing a mixture of a hard metal powder and a carrier;    -   B. heating the mixture;    -   C. extruding the heated mixture in a feed direction through a        die which forms the mixture with a cylindrical outer surface;    -   D. conducting the mixture past a flute-forming structure which        forms a chip flute along a first section of the outer surface;    -   E. displacing the flute-forming structure laterally away from        the outer surface during step C for terminating the chip flute        formation along a second section of the outer surface which        defines a shank portion;    -   F. allowing the mixture to solidify and form a blank; and    -   G. sintering the blank.

The apparatus is adapted to be mounted to an extrusion machine forshaping a mixture received from the extrusion machine into a rotary toolfor chip forming machining. The apparatus comprises a housing which isadapted to be mounted to an extrusion machine and forms athrough-passage for conducting the mixture in a feed direction. Thethrough-passage defines a center axis. A nozzle is provided which formsa restriction in the passage. A die is disposed downstream of the nozzleand includes a through-hole. At least one jaw is situated adjacent adownstream end of the die and is movable toward the axis to an innerposition in engagement with the mixture received from the die forapplying a shape thereto. The die is movable away from the axis to anouter position to avoid applying the shape thereto.

The invention also pertains to a rotary tool made by the above-describedmethod.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become apparent fromthe following detailed description of a preferred embodiment thereof inconnection with the accompanying drawings in which like numeralsdesignate like elements and in which:

FIG. 1A is a side elevational view of drill made according to thepresent invention;

FIG. 1B is a front perspective view of the drill depicted in FIG. 1A;

FIG. 1C is a rear perspective view of the drill depicted in FIG. 1A;

FIG. 2A is a front view of an apparatus according to the presentinvention;

FIG. 2B is a sectional view taken along the line IIB—IIB in FIG. 2A;

FIG. 2C is a rear end view of the apparatus depicted in FIG. 2A;

FIG. 2D is a sectional view taken along the line IID—IID in FIG. 2A; and

FIG. 3 is a view of the apparatus shown in FIG. 2B attached to anextrusion machine.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The preferred embodiment of a tool according to the invention shown inFIGS. 1A–1C is a so-called helix drill. The drill 10 is solid and madeof hard material, such as extruded hard metal (e.g. carbide), andincludes helical chip flutes 18, and a non-fluted shank 11 adapted to besecured to a rotary spindle, not shown. The drill has two upperclearance surfaces 15. All surfaces and associated edges are made fromthe same material, i.e. preferably in extruded hard metal. Lines ofintersection of the chip flutes 18 and the clearance surfaces 15 formmain cutting edges 19, preferably having reinforcing chamfers, notshown. The entire length of the drill is from 3 to 10 times itsdiameter. Two flush channels 14 extend through the entire drill totransfer flushing medium from the spindle to the tip of the drill. Adiametrical groove has been provided at the rear end face of the shankto counteract obstruction of the holes, for example.

In FIGS. 2A–2D there is shown a device 20 according to the presentinvention for the production of elongated green bodies. The device 20comprises a rectangular steel housing 21, which is intended to befastened by, for instance, bolts to an extrusion machine 50 (see FIG.3). The housing 21 has two bolts 22 to be fastened in the machine andhas a rear surface 23 intended to seal against said machine. The housinghas a central through-going recess 24 through which a compound will bepressed. The recess 24 is widened at the rear surface 23 to form spaces25, 26 for receiving two feed worm 53 ends, FIG. 3. The recess 24transforms into a diameter-reducing restriction 27 in a circular nozzle28. The nozzle 28 is made from a wear resistant material such as hardmetal. The recess 24 then continues via a cylindrical inner, centrallypositioned hole 30 into a circular die 29, which is provided next to thenozzle 28. The position of the die 29 relative to the housing isdetermined by cooperation between a stop screw 31 in the housing and ahole 32 in the die extending laterally relative to the principal feeddirection F of the compound. A bar-shaped core 33 is disposed in thedie. The core is rectangular and includes two holes 34 to receiveelongated pins 35. The pins 35 are intended to project from the core inthe feed direction F in case flush channels are to be formed in theblank. The recess 24 then continues in the form of a coaxial hole 37 ina lid 36. The lid 36 is attached to the housing by means of two screws38 and screws 22. The lid 36 is provided with a groove 39, which extendsbetween two long sides of the lid 36. The groove 39 is intended toreceive a jaw structure comprised of two jaws 40, 41, which togetherform a T-shape, see FIG. 2B. The jaw structure includes an open inletand an open outlet through which the extrudate passes upon exiting thedie, the open inlet and open outlet being of substantially the samesize. Each jaw 40, 41 includes a recess 42 facing towards the other jaw.Each recess 42 includes a helical ridge 43 shaped to form a chip flutesuch that when the jaws are pressed against each other the recesses formthe cross-section of a helix drill having chip flutes. The jaws arepressed against each other in a radial direction, i.e. laterally of acenter axis of the device, by suitable power means, not shown, and thesame power means is also used to displace the jaws radially away fromone another in the groove 39, such as when a portion of the extrudedblank must be non-fluted, for example the drill shank portion 11.Preferably a supporting table is placed in connection with the jaws tosupport the hot extruded blank.

The drill or the milling cutter is manufactured as follows. Hard metalpowder having a certain cobalt content and a carrier, for example apolymer or a plastic, is mixed and shaped into pellets or granulates.The content of binder lies within the interval of 1–10 percent byweight. The expression “cobalt” shall here be understood as a metallicbinder that alternatively can be exchanged for or include other metals,for example nickel, Ni. Subsequently the mixture or compound ispreheated to a temperature suitable for the particular mixture and isinserted in an extrusion machine 50. The machine 50, see FIG. 3,includes a funnel 52 to receive pellets, two feed worms 53 rotatable bymeans of a motor in a casing 55, and heaters 54. Then the mixture ispressed into the recess by means of the two feed worms 53 at a certainpressure and a certain temperature, i.e., about 180° C., that isconsiderably lower than in the prior art where the melting temperatureof cobalt is required. The restriction 27 will further compress themixture or compound.

Then the hot compound reaches the core 33 and passes along oppositesides thereof through the two substantially semi-circular openingsformed at respective ones of the sides. Rearwardly (downstream) of thecore in the feed direction F the compound fuses into a cylindrical body.If the pins 35 are provided in the core, then spaces are formed in thebody, which later will constitute flush channels. The pins are made longenough to allow the compound to cool such that fusion within the flushchannels is avoided. Subsequently the compound reaches the jaws 40, 41which are disposed in an inner position. The compound travels throughthe recesses 42 defined by the jaws 40, 41 whereby the compound, due tothe geometries of the ridges 43, travels helically through the jaws andobtains the cross-section of a helix drill. The ridges 43 need not beidentical. When the compound comes out from between the jaws it coolsquickly due to the surrounding temperature, and the blank continues toextrude until the fluted part is sufficiently long. Subsequently thejaws 40, 41 are radially separated to outer positions away from thecompound such that a cylindrical non-fluted shank portion is formed. Thelength of the shank part is determined either by how long the extrusionis continued or by when the jaws are displaced inwardly such that theformation of a new blank is initiated. In the latter case two or moreblanks are continuous. The solidified blank can then be cut or simply bebroken, for example by hand, into suitable lengths, e.g., in intervalsof 5–10 times its diameter.

Then the blank is heated in a separate furnace such that the carrier isburned off and such that the binder metal melts and binds the carbides.Then further machining takes place, such as grinding for example at edgeportions, shank portion and clearance surfaces.

With the present method and device a tool can be produced with orwithout chip flutes and with or without a shank portion and allows asimple handling to a low cost. This can be done without generating dust.Furthermore unsuccessful blanks can simply be remilled and recycled inthe extruder. In addition, at least one jaw could be used to make marksin the shank portion of the blank where a plane is to be ground forchucking. Thereby the grinding volume can be minimized.

The invention is in no way limited to the above described embodimentsbut can be varied freely within the scope of the appended claims. Thusthe invention can be used also for making solid end mills. The tool canbe coated with layers of for example A1₂O₃, TiN and/or TiCN.

1. An apparatus adapted to be mounted to an extrusion machine andincluding an extrusion passage for shaping a mixture received from theextrusion machine into a rotary tool for chip forming machining, theextrusion passage defining a center axis, the apparatus comprising: ahousing adapted to be mounted to an extrusion machine; a nozzle disposedin the housing and forming a restriction in the extrusion passage; a diedisposed in the housing downstream of the nozzle and forming a portionof the extrusion passage; and a jaw structure situated adjacent adownstream of the die in an inner position defining a portion of theextrusion passage and including an open inlet and an open outlet throughwhich the mixture axially passes upon exiting the die, the jaw structurehaving at least one jaw including a shaping element arranged to form ashape in an outer periphery of the mixture as the mixture travelsaxially therepast, the at least one jaw being movable in a directionaway from the center axis to an outer position out of engagement withthe mixture to avoid applying the shape thereto, wherein the open inletand the open outlet defined by the jaws disposed in their inner positionare of substantially the same size, wherein the die includes athrough-hole of circular cross-section, and further including a coredisposed in the passage upstream of the circular cross-sectionthrough-hole, and wherein the core is rectangular and a pair of pinsproject from the core in the feed direction for forming flush channelsin the tool.
 2. An apparatus adapted to be mounted to an extrusionmachine and including an extrusion passage for shaping a mixturereceived from the extrusion machine into a rotary tool for chip formingmachining, the extrusion passage defining a center axis, the apparatuscomprising: a housing adapted to be mounted to an extrusion machine; anozzle disposed in the housing and forming a restriction in theextrusion passage; a die disposed in the housing downstream of thenozzle and forming a portion of the extrusion passage; and a jawstructure situated adjacent a downstream of the die in an inner positiondefining a portion of the extrusion passage and including an open inletand an open outlet through which the mixture axially passes upon exitingthe die, the jaw structure having at least one jaw including a shapingelement arranged to form a shape in an outer periphery of the mixture asthe mixture travels axially therepast, the at least one jaw beingmovable in a direction away from the center axis to an outer positionout of engagement with the mixture to avoid applying the shape thereto,wherein the open inlet and the open outlet defined by the jaws disposedin their inner position are of substantially the same size, wherein theat least one jaw comprises a plurality of jaws each including a recessfor conducting the mixture, the shaping element comprising a helicalridge disposed in the respective recess for contacting the mixture whenthe jaws are in the inner position, for forming helical chip flutes inan outer surface of the tool.
 3. Apparatus adapted to be mounted to anextrusion machine for shaping a mixture received from the extrusionmachine into a rotary tool for chip forming machining, the apparatuscomprising: a housing adapted to be mounted to an extrusion machine andforming a through-passage for conducting the mixture in a feeddirection, the through-passage defining a center axis; a nozzle forminga restriction in the passage; a die disposed downstream of the nozzleand including a through-hole; and at least one jaw situated adjacent adownstream end of the die and movable toward the axis to an innerposition in engagement with mixture received from the die for applying ashape thereto, the jaw being movable in a direction away from the centeraxis to an outer position out of engagement with the mixture to avoidapplying the shape thereto, wherein the die through-hole is of circularcross-section, and further including a core disposed in the passageupstream of the circular cross-section through-hole, wherein the core isrectangular and a pair of pins project from the core in the feeddirection for forming flush channels in the tool.
 4. The apparatusaccording to claim 3, wherein the at least one jaw comprises a pluralityof jaws each including a recess for conducting the mixture, each jawincluding a helical ridge disposed in the respective recess forcontacting the mixture when the jaws are in the inner position, forforming helical chip flutes in an outer surface of the tool. 5.Apparatus adapted to be mounted to an extrusion machine and including ashaping passage for shaping a mixture received from the extrusionmachine into a rotary tool for chip forming machining, the passagedefining a center axis, the apparatus comprising: a housing adapted tobe mounted to an extrusion machine; a nozzle disposed in the housing andforming a restriction in the passage; a die disposed in the housingdownstream of the nozzle and forming a portion of the passage; and a jawstructure situated adjacent a downstream of the die in an inner positiondefining a portion of the shaping passage and including an open inletand an open outlet through which the mixture axially passes upon exitingthe die, the jaw structure having at least one jaw including a shapingelement arranged to form a shape in an outer periphery of the mixture asthe mixture travels axially therepast, the at least one jaw beingmovable in a direction away from the center axis to an outer positionout of engagement with the mixture to avoid applying the shape thereto,wherein the die includes a through-hole of circular cross-section, andfurther including a core disposed in the passage upstream of thecircular cross-section through-hole, the core being rectangular and apair of pins project from the core in the feed direction for formingflush channels in the tool.
 6. Apparatus adapted to be mounted to anextrusion machine and including a shaping passage for shaping a mixturereceived from the extrusion machine into a rotary tool for chip formingmachining, the passage defining a center axis, the apparatus comprising:a housing adapted to be mounted to an extrusion machine; a nozzledisposed in the housing and forming a restriction in the passage; a diedisposed in the housing downstream of the nozzle and forming a portionof the passage; and a jaw structure situated adjacent a downstream ofthe die in an inner position defining a portion of the shaping passageand including an open inlet and an open outlet through which the mixtureaxially passes upon exiting the die, the jaw structure having at leastone jaw including a shaping element arranged to form a shape in an outerperiphery of the mixture as the mixture travels axially therepast, theat least one jaw being movable in a direction away from the center axisto an outer position out of engagement with the mixture to avoidapplying the shape thereto, wherein the at least one jaw comprises aplurality of jaws each including a recess for conducting the mixture,the shaping element comprising a helical ridge disposed in therespective recess for contacting the mixture when the jaws are in theinner position, for forming helical chip flutes in an outer surface ofthe tool.